moisture content of wood and RMH's

I've seen 'discussion' about the efficiency of the RMH. The moisture content of the wood may make the math work better for the number crunchers out there.

With all other wood burning stoves (for house heating) you insert the wood and then burn the stove. If the wood has 10% moisture and you put 10 pounds of wood in the stove you have actually placed 9 pounds of wood and 1 pound of water. It takes a considerable volume of energy to boil water and that energy is taken out the chimney in the form of steam. This is why it is so important to have dry wood. It takes almost 1000 btu’s to boil 1 pound of water plus the energy to get it to the boiling point. That is the amount of energy in ¼ to ½ pound of wood. Our 10 pounds of wood is now down to 8.5 pounds of heat producing wood. I'd guess that boiling off the water also decreases the efficency of the burn.

With a RMH the wood feeds into the stove. As the wood feeds towards the stove it has a chance to dry out before going into the combustion chamber. If the wood completely dried out then the preverbal 10 lbs. of wood would actually be 10 lbs of heat producing wood and would give RHM a 15% advantage in this theoretical comparison.

I’ve seen a few threads where people are trying to get their heads around the efficiency differences between RMH and other wood stoves. I haven’t seen this topic discussed.

Paul Ely : There is something in what you say, but lets look at the other end. The wood stoves that the E.P.A. is rating as having an efficiency of around 85%
have to have an Exhaust gas temperature of 500f to receive their little E.P.A. TAGS, our rocket stove with a exhaust temperature of less then 212 f has turn
-ed that 'Latent heat of Evaporation' on its head. As the temp drops below 212f in the horizontal pipes in our thermal mass we can see that we are gaining all
that back because of the condensed steam seen at the Exhaust !

Peter Clouston warns that the water vapor that gets absorbed within the thermal mass will seek equilibrium with the water vapor in the room, if the rooms
water vapor % is lower, then water vapor will leave the Cob and we start the cycle over again evaporation into the room and condensation on cold surfaces!
This increase in water vapor in the room makes the air in the room feel warmer, but not-so-much after about 70% ! Bad news in the middle of the winter for
people in the pacific Northwest !

For the Future of the Craft ! Be safe, keep warm ! PYRO-LOGICAL Big AL ! - As always, your comments / questions are solicited, and are Welcome A. L.

Science and Math are our language for ATTEMPTING to describe reality. This language is not fully developed. I’m an engineer by schooling and once I understood this fact it helped me considerably. RMH work – now can we figure out how to make the math describe this reality.

Yes, if the steam is condensing inside of the house then that heat would be realized inside of the house.

Paul Ely wrote:
you have actually placed 9 pounds of wood and 1 pound of water.

No.
You have actualy placed about 4 pounds of carbon and about 6 pounds of water.

Wood is made up from long chains of sugar.
Ash neglected (1%).

C6H12O6 ~ 180.16 g/mol

C ~ 72.06g
H ~ 12.16g
O ~ 96.00g

C2 ~ 72.06g
H2O ~ 108.10g

At 10% moisture per kilo

Carbon 360g
Water 640g

Karol Kerl : W.O.W., high school chemistry,and I ducked out and went to vocational school. Lets play the game, for every mole of Carbon we need 2 moles of Oxygen,
and we need 2 moles of Hydrogen for every Mole of Oxygen so most of the 'new molecule' arrangements are CO2, but not by weight ! once we think heavy thoughts -
Like where did I put THAT book we can figure out true proportions of CO2 and H2O by weight adding in the 10% at the end .

O.K. all you chem 101s how did I do! For the Future Good of the Craft! Be safe, keep warm! As always, questions/comments are solicited and are Welcome PYRO AL

allen lumley wrote:Karol Kerl : W.O.W., high school chemistry,and I ducked out and went to vocational school. Lets play the game, for every mole of Carbon we need 2 moles of Oxygen,
and we need 2 moles of Hydrogen for every Mole of Oxygen so most of the 'new molecule' arrangements are CO2, but not by weight ! once we think heavy thoughts -
Like where did I put THAT book we can figure out true proportions of CO2 and H2O by weight adding in the 10% at the end

Wood with an extremely high energy content.
Very raw calculation

Cellulose ~ 68.5%
C12H22O11 ~ 342.30 g/mol

Lignine ~ 28.5%
C10H12O3 ~ 180.20 g/mol

Terpene ~ 3%
C5H8 ~ 68.12g/mol


C822 H1507 O754
C685 H822 O205
C342 H548

C2H3O1 ~ 43.04

C2 ~ 24.02g ~ 55.80%
H2O ~ 18.02g ~ 41.86
H2 ~ 1.00g ~ 2.32

At 10 % moisture:
Carbon one pound
Water one pound

This Calculation was very sloppy.

A bit more precicely.
Cellulose ~ 63.5%
C12H22O11 ~ 342.30 g/mol

Lignine ~ 33.5%
C10H12O3 ~ 180.20 g/mol

Volatile ~ 3%
CH4

C23 H38 O14 ~ 538.5 g


C2 ~ 276.24g ~ 51.3%
H2O ~ 252.21g ~ 46.8%
H2 ~ 10.05g ~ 1.9%

At 10 % moisture:
Carbon 46%
Water 54%

Karol Kerl ; I freely admit that I am over my head here. I was only able to follow this stuff by-the-book before my T.B.I. . But, I think we are on the opposite sides of
the by volume, by weight thing and perfect mixtures! I am looking at a bottle of rubbing Alcohol that states it is 91% isopropyl by weight, by volume its closer to 70%!

For the future good of the Craft ! Be safe, keep warm ! Pyro-logical Big AL - As always your comments and questions are solicited and Welcome ! A. L.

allen lumley wrote:
I am looking at a bottle of rubbing Alcohol that states it is 91% isopropyl by weight, by volume its closer to 70%!

It is the other way round.

Anyway.
In the best possible case the total content of water is 1/2 and 2/3 in the worst.
Thus the amount of latent heat, which could be recovered by condensation, is a lot higher as people may think.

karol,
so when the water goes through a rocket stove at a high temp, does it break down into O2 and H? And if so do they not add fuel to the mix?

I have been burning and heating with wood for almost 20 yrs.not sure about how rocket stoves react to wet or green wood,but i do know that burning to much green or wet wood in a conventional wood stove causes creosote build up in the pipe and can be dangerous.If the wood is green I always allow more incoming air into the stove and open up damper,not exact science but some backwoods wisdom.

Charlie Woodsman : Welcome to Permies, with over 16,000 registered members checking in regularly there is a lot of knowledge in these Forum Threads ! Come over to
the Rocket Stoves Forum and see what you can learn about this combination of old and new technology ! Two points, because this stove works best with small wood, and
can not be choked down to 'hold a fire over night' Creosote and Chimney fires are virtually unknown ! Besides burning at close to the temperature that glass melts at,
making for a very efficient burn, the Rocket Mass Heaters' R.M.H.s' Thermal mass heat storage rivals the best masonry heater Costing Thousands of dollars and can be a
D.I.Y. project!
For the Good of the Craft ! Be safe, keep warm ! PYROLOGICAL Big AL ! - As always your comments and questions are solicited and are Welcome ! A. L.

Miles Flansburg wrote:karol,
so when the water goes through a rocket stove at a high temp, does it break down into O2 and H? And if so do they not add fuel to the mix?

One would have to mix wood dust with dust of some metals like aluminum or magnesium to get temperatures around 3000°C,
while offering something more attractive than hydrogen for marriage with oxigen.
Would destroy the RMH very fast.

Replacing a weaker bond by a stronger bond releases more energy as needed to break the weaker.
That's why something burns.

Karol Kerl : Yes, you are correct about Reactions needed to get temperatures in the 3000C range. I had a lot of fun helping a local Hacker-Space group launch an Alice / Al-ice
Rocket and we melted/consumed part of the throat of our rockets nozzle !

In my original post I used the layman's term 'melt' to describe the re-liquifycation of glass! ( There is presently a little Kerfluffle about whether glass actually 'melts' at all ! )

The temperature that ground quartz silica liquifies at IS ~ 1723C ~ - ~ 3133C ~ ! Re-'melting' glass Temperatures can be as low as 650C, but I would freely agree
that ~ 1400C ~ is a more median temperature ! I'm sorry if it looked as though I was trying to 'Cherry Pick' my facts !

I apologize for the confusion my generalized use of laypersons terms has caused - However, with the not uncommon finding of fused Rock Wool Insulation and sintered Fly Ash
, we are seeing temperatures in those ranges !

For the Future/Good of the Craft ! Be safe, keep warm ! PYRO-LOGICAL Big AL ! - As always, your comments and questions are solicited and are Welcome ! A. L.

Last weekend I went up to a Cabin we have in Northern Wisconsin. One mile walk in to our place off of the blacktop road. We had not been into the place for several months. It is a basic cabin we were working on. (Although it had electric in it and a basic emergency Propane space heater).
All this information people put on this thread, But the moisture really has a hard time getting thru a horizontal pipe. Here is something that happened to me. There must be other people who share their ACTUAL EXPERIENCE about moisture in pipes,

Went to our cabin.
I arrived at 8pm it was dark and 20 degrees. My plan was to turn on the lights and get a propane heater going to take the chill off the place and settle in for the night. Well so much for that. Someone had broke in and stolen the copper wire on the walls and stolen the small propane tanks.
I hauled an old barrel wood stove into the place,opened a window cut a hole in a piece of plywood with a handsaw to get a exhaust pipe set up. The pipe came out of the flange on the berrel stove. Had a 12" vertical rise to a 90 elbow to horizontal pipe which was 60" long to another 90 elbow and then vertical pipe 9 feet up. This is all the pipe I had to work with. everything was non insulated pipe. At first I had some smokeback. But once I got the fire going it was ok. I used this stove to heat the place for 8 days while I stayed there and worked on the place.
Now the wood that was available to me was not green wood. Much of it was old firewood that had been covered for several years and some had been cut up 6 months earlier. It was not completely Dry wood and had a bit of moisture. The fire lasted all night, had full flame and a slight cool down from full burn at about 4am. It kept red hot coals until 5-6am. The stove pipe I used was a mix match of pipes a few drilled holes in the walls. About 4 am I heard water dripping out of a hole in the horizontal pipe. I put a bucket under it, At first I thought it was from show that was dripping down. But No it was coming out of the exhaust pipe. It would drip out a half of a gallon of black water each morning at the same time.
I hear all of the stories of 20 feet plus horizontal pipes before your vertical pipe. This is the first time I have used such a long horizontal pipe on any wood stove. Makes me wonder how some people say this only steam. Heck this was a half a gallon of water that would come out every morning at about 4 am of this pipe every day.
If anyone has any comments about my actual experience last week, Please make comments from your Actual experiences on moisture and not just information you read in a book sometime . I am guessing the pipes need to be insulated in this application. but thats a lot of water to end up in a bucket every day.It was the only pipe I had available to me. It has been disassembled and will never be used this way again up there.

Sorry my click and paste of the story came out poorly. But you get the story.

Jeremial Wales : As previously stated Water vapor condensation within the horizontal pipes of a Rocket Mass Heater R.M.H.,is expected and looked for Visual
proof that the internal temperature is below 212 f giving us back the Latent heat of Vaporization, hopefully without accumulation !

I am totally unable to explain the large amount of water noted in your report on your experience with an unusual 8 day heating adventure though it is interesting,
Your report the accumulation of a half gallon of water between 4am and 'Morning', followed by other accumulations by morning of following days ! With 10% water
content in your wood you would have to have burned more than 40 Lbs. of wood shortly before 4am and morning, with similar results over the next few days as
reported by you ! Though I was not there I find my mind trying to come up with an alternative explanation for at least part of the water !

I am interested in trying to give you good Third party use and direct knowledge of use of R.M.H.s, with the understanding that those of us who have lived with this
system CAN NOT BE unbiased !

Please look in the R.M.H. playlist for - ' Two more great working Rocket Mass Heaters - - - - -. The first video is your direct evidence of R.M.H. use through this
last heating season. I assisted Ernie and Erica Wisner during their Northern New York Workshop where this was built last fall ! The 8'' system was approximately 30 '
long with 5 Elbows / Clean outs before the triple wall stove pipe interior chimney left the house. The whole winters worth of fly ash was collected without any noticeable
water moisture accumulation !

Finding other third party reports to share may take some time, I will keep looking, another heating season is coming ! Big AL your comments questions are welcome !

First Hand information in plain english is the best that we can all hope for here. Actual experience with wood stoves is very needed. Hope that more people would share actual facts that they have had experience with.